International Journal on Electrical Engineering and Informatics ‐ Volume 4, Number 1, March 2012 Digital Two Dimensional (2D) Implant Design for Pre-operative Planning
in Total Hip Arthroplasty
Azrulhizam Shapi’i1, Riza Sulaiman2, Mohammad Khatim Hasan3, Anton Satria Prabuwono4,
and Abdul Yazid Mohd Kassim5
1.2.3.4
Industrial Computing Research Group, Faculty of Information Science and Technology,
Universiti Kebangsaan Malaysia, 43600 Bangi Malaysia
5
Medical Center of Universiti Kebangsaan Malaysia,
Bandar Tun Razak, 56000 Cheras, Kuala Lumpur, Malaysia
1
azrulhizams@gmail.com, 2rs@ftsm.ukm.my, 3khatim@ftsm.ukm.my,
4
antonsatria@ftsm.ukm.my, 5dryazidk@gmail.com
Abstract: Pre-operative planning is very important in the process of a Total Hip
Arthroplasty (THA) because it is a method for determining the size and optimal implant
position. According to experts from Medical Center of Universiti Kebangsaan Malaysia
(UKMMC), manual methods are still used to find a suitable implant size for the patient.
By using the manual method, any error in template transformation such as rotating and
scaling while recording the patient's hip bone radiographs prior to the surgery will lead
to errors in determining the size of implant templates. Therefore, a digital method
should be developed so that the implant size detection process can be effectively
implemented. Manual implant template used by UKMMC is using as the basis for the
hip joint implant design. This template is redesign using AutoCAD 2010 software.
Template generated in AutoCAD format will be converting to JPEG format so that it
can be used in Adobe Photoshop software for colouring and scaling. A total of ten Xray patients were randomly selected to test the accuracy and effectiveness of the digital
implant. Results showed this digital technique predicted stem component size well, with
80% within ±1 size and acetabular component was predicted slightly better with 90%
within ±2 component size.
Keywords: Computer Aided Design (CAD), digital, templating, total hip arthroplasty
(THA), implant.
1. Introduction
Over the past decade, computers have revolutionized medical imaging [1]. At present, the
field of digital and computer technology has experienced a rapid development. It includes
integrated technology to achieve, store and disseminate information in various forms such as
text, sound, images, graphics, and animation. The use of computer technology is no longer
limited to the professional sectors, but also to the health sector. Computer is used to help
people move out tasks effectively and efficiently.
Design can be defined as new ideas developed in a painting such as drawing geometry,
engineering and plans [2]. In product development, process design is the most critical
process for any product to be produced should meet the specifications and in accordance with
the requirements and demands of consumers. The design can be either a new process design or
modifying the existing design. Design process using a computer is now simplified with
extensive software which helps to improve design productivity and produces high quality
design, as well as to reduce the development of a product. Among the software used in design
work, are AutoCAD, MasterCAM, NX5, Solidworks and others.
Total hip arthroplasty (THA) or Total hip replacement (THR) is the most successful and
most effective surgery in the world [3]. Success rate of this surgery in experienced medical
Received: February 24th, 2011. Accepted: December 15th, 2011
67
Azrulhizam Shapi’i, et al.
centres were within 95%. The initial impact of this surgery is loss of joint pain as soon as
leaving the surgery. Patients will be able to run again after two to three days and the patient
can leave hospital within six to seven days after surgery. In THR, preoperative planning with
overlying templates has become an indispensable part of modern THA, and numerous methods
have been proposed for its implementation [4]. With better surgical techniques, aided by the
use of computer and sophisticated equipment, THA at a later time will be complete within one
day.
As digital technology improves and becomes more accessible to the health care industry,
digital preoperative planning will be used by an increasing number of medical centers. More
practices will become filmless and software will be necessary for successful templating. The
digital implant design should be produced because it will benefit the medical sector,
particularly in the orthopaedic field [5].
2. Objectives
• To produce a digital implant design for total hip arthroplasty using AutoCAD 2010
software.
• Implant design in two dimensions (2D).
• Implement digital implants produced on X-ray images digitally (DICOM data).
3. Research Background
The two important subjects that will be discussed are the designation of implants process
and total hip arthroplasty procedure. These two things are extremely important as they play
significant roles in the production of a good and effective digital implant design.
A. Computer Aided Design
Computer Aided Design or CAD can be defined as the usage of computer hardware and
graphics software in assisting the production of product design from the first stage i.e the
concept level through to the level of documentation [6]. CAD is a design activity that involves
the use of computers to create, modify and document engineering design [7]. It is also a
creation and manipulation activity of a drawing or computer engineering design. CAD
produces more efficient design documentation and resulting in the creation of manufacturing
database which can save time in product design development.
Skills in CAD area are very important in carrying out this study. Designing processes need
to be done carefully so that the digital implants produced can be used effectively. In addition,
the knowledge of the hip joint replacement should be prioritized. This is necessary because we
need to know the type and size of the implants involved.
B. Total Hip Arthroplasty (THA)
Total hip arthroplasty (THA) is a process in which the hip joints are replaced with artificial
joints or implants. According to [8], THA is a surgical procedure that replaces the diseased
cartilage and joint with artificial materials made of metal and plastic. The use of these implants
is intended to help the patients lead a normal life without any interference or pain in the joints
when walking and performing daily activities. Anatomically, the hip joint is comprised of a
ball and socket joint. The socket is comprised of pelvic bones shaped like a cup, known as the
acetabulum, which is connected to the end of the femur, which is shaped like a ball.
The three main components involved in THA are the stem, acetabular and ball. The
corresponding artificial components are designed to ensure that the metal will always rub on
the plastic and result in a gentle movement with minimum erosion [4]. In another words, an
artificial hip joint (prosthesis) is made up of a ball and socket that fit together to form a joint
very similar to patient’s hip. Figure 1 shows the implants used in THA [9].
68
Digital Two Dimensional (2D) Implant Design for Pre-operative Planning in Total Hip Arthroplasty
Figure 1. THA implant
A hip prosthesis or implant consists of the same basic parts as a human hip joint. The
various types of implants are made up of metals or ceramics and plastics. The worn hip socket
is replaced by a cup and the worn head of the thigh bone (femur) is replaced by a ball. The ball
is attached to a stem that is inserted into the thigh bone for stability. While the prosthesis can
restore hip movement, an artificial hip usually has a more limited range of motion than a
healthy hip joint. Figure 2 shows the position of the implants after THA is performed [10].
Figure 2. Position of the implants
69
Azrulhizam Shapi’i, et al.
C. Manual Pre-operative Templating
Pre-operative templating is an important part of a total hip arthroplasty [11]. The implant
template preparation prior to surgery is important in the process of patient screening, in which
the surgeon can determine the optimal implant size before surgery [4]. Normally the surgeon
will perform the implant template customization and then bring the results to the operating
room before making a final selection of the appropriate implant size. For the conventional
method, any error in rotation and scaling during skeletal/skeleton radiograph recording before
surgery will result in significant errors in determining the implant size [5]. Hopefully, the use
of digital implant will help the surgeon to make more effective decisions. Figure 3 and figure 4
shows the manual implant template used in THA.
Figure 3. Stem implant template
Figure 4. Acetabular implant template
70
Digital Two Dimensional (2D) Implant Design for Pre-operative Planning in Total Hip Arthroplasty
4. Implant Design Methodology
To conduct this research, the methodology used is based on the approach of 'RAPID
Application Development' (RAD). RAD life cycle includes four phases: planning, analysis,
design and implementation. Figure 5 shows a simple flow chart of a sequence of steps needed
to produce the digital hip joint implant
Figure 5. Design methodology for hip implant
The result of this research is the digital implant design for THA procedure. Important tool
involved in the design is a two-dimensional (2D) sketch view using AutoCAD software. The
environment and functions in AutoCAD 2010 software enables the 2D model to be produced
easily and has a similar form with a real hip joint implant.
A. Two Dimensional (2D) Implant Design
The prerequisite of designing a stem is to model the shape of the stem implant [12]. The
basic design of total hip’s implant can be seen in figure 6 and figure 7.
Figure 6. Stem basic design
71
Azrulhizam Shapi’i, et al.
Figure 7.
7 Acetabular basic design
2 implant skeetch is producced using AutooCAD 2010 software.
s
2D
D views are ass
The 2D
shown in figure 8 and figure
f
9. Three views shownn in the 2D draawing using thhe viewport aree
w, Left View an
nd SE Isometric View. Usagge of viewport function helpss in getting thee
Top View
views froom various diirections. Skketches are drawn with thee aid of primiitive entity inn
AutoCAD
D 2010 softwarre such as Linee, Polyline, Recctangle, Circlee, Elipse Arc annd others. Thee
commandds used to com
mbine primitivee entity to maake a complex 2D view are Move, Rotate,,
Scale, Breeak, Join, Filleet and others.
Figurre 8. Stem impllant design
Figure 9.
9 Acetabular im
mplant design
72
Digital Two Dimensional (2D) Implant Design for Pre-operative Planning in Total Hip Arthroplasty
The CAD
C
file is th
hen converted into JPEG forrmat so that it
i can be usedd in Photoshopp
software to further beaautify the impplant. By usingg Photoshop, the digital im
mplants can bee
coloured with any apprropriate colourrs. Digital impplants produceed using Photooshop softwaree
can be seeen in figure 10 and figure 11..
Figure 10. Digital acetabulaar implant for THA
T
mplant for THA
A
Figure 11. Digital stem im
5. Resultt and Discussiion
Digitaal templating is
i the preparation process off the pre-surgeery scenario byy using digitall
implant that
t
designed in this studyy. Digital im
mplant can be manipulated as a tool forr
measurem
ment and artifi
ficial templatess for orthopaeedic surgery [13]. Digital implant usagee
enables suurgeons to seleect implant andd do the compuuterized pairingg. The surgeon performs thee
necessaryy measuremen
nts on the tem
mplate and executes surgiccal planning in the digitall
environm
ment. Figure 12
2 and figure 133 shows the usee of digital impplant in total hip
h arthroplastyy
pre-operaative planning.
To tesst the effectiveeness of the digital implants,, testing with actual
a
cases haas been carriedd
out in coooperation witth orthopaedicc specialists frrom the Univversiti Kebangssaan Malaysiaa
Medical Centre
C
(PPUK
KM). A total nuumber of 10 acctual cases of patients who had
h undergonee
THA are used for testin
ng purposes. Teesting with acttual cases has been
b
implemennted because itt
plays an important rolee in determininng the effectiveeness of the diigital implant. Results of thee
b the digital technique are compared
c
to thhe implant size used in actuall
implant siize produced by
cases. Figgure 14 shows the example off an X-ray imaage of a patientt who has undeergone total hipp
arthroplassty surgery.
73
Azrulhizam Shapi’i, et al.
Figure 12. The use of digital implant in THA (left hip)
Figure 13. The use of digital implant in THA (right hip)
74
Digital Two Dimensional (2D) Implant Design for Pre-operative Planning in Total Hip Arthroplasty
Figure 14. Total hip arthroplasty actual case
For each X-ray sample, the optimal implant sizes determined by both manual and digital
methods were recorded. The difference between the two sizes was calculated and shown in
Table 1. It is evident that the digital technique yields very close results to those obtained
through the conventional method in all ten studies. The difference, if any, is also within the
error of clinically acceptable range (±1 mm size for stem, ±2 mm for acetabular) obtained
through the manual templating method. In addition, the study also demonstrated that the
average time taken for implant templating in THA pre-operative planning using the digital
technique was much less than when using the manual method.
Table 1. Manual vs digital
Cases
Stem
(Conventional)
Stem
(Digital)
Diff.
Acetabular
(Conventional)
Acetabular
(Digital)
Diff.
1
12
10
±2
48
48
0
2
11
11
0
54
52
±2
3
12
11
±1
50
50
0
4
13
13
0
52
52
0
5
15
17
±2
46
46
0
6
12
12
0
48
46
±2
7
16
15
±1
52
56
±4
8
13
13
0
58
56
±2
9
11
11
0
56
56
±2
10
15
15
0
54
54
0
6. CONCLUSIONS
AutoCAD is highly skilled software in performing drawing works. AutoCAD usage is
extremely useful in designing digital implant for the hip joint. The research shows that the
AutoCAD 2010 software is highly potential in producing a detailed and complex product
design. At present, the AutoCAD usage is not only limited to the field of manufacturing and
architecture, but it can also be used in the medical field. The production of this implant allows
it to be used in the digital environment.
75
Azrulhizam Shapi’i, et al.
The digital implant provides several advantages for THA surgery. Compared to the manual
method in which the surgeon uses a template manually and place it on the patient’s X-ray , the
use of digital implant not only saves time, but it also can reduce the error due to consistency
difference when making adjustments to patient’s implant size [14-16]. In addition, by using
digital implant, it can be manipulated easily such as doing rotation and scaling. The digital
method, if being use properly will enable to help surgeons to make decisions accurately and
effectively. Based on the testing results, the digital implants produced were suitable and can be
used in the digital environment.
Acknowledgment
This research project was conducted in collaboration with Dr Abdul Yazid Mohd Kassim from
the Department of Orthopaedic and Traumatology and Dr Hamzaini Abd Hamid from the
Department of Radiology, Medical Centre of University Kebangsaan Malaysia. This research
was also funded by the University Grants UKM-OUP-ICT-35-179/2011 and UKM-GUPTMK-07-01-035.
References
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Digital Two Dimensional (2D) Implant Design for Pre-operative Planning in Total Hip Arthroplasty
[16] Vallle A.-G.; Comb
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(SIC
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Azrulhizam Shapi’i is currently pursuing Ph.D
D in Industrial Computing att
K
M
Malaysia.
He iss
School of Information Technologyy, Universiti Kebangsaan
ng as Lecturerr in the School of Informatioon Technologgy , Faculty off
workin
Inform
mation Science and Technologgy, University Kebangsaan Malaysia.
M
He iss
an autthor and co-auuthor for moree than 30 scienntific papers inn Internationall
Journaals and Conferrences. His ressearch areas of
o interest incllude Computerr
Aided Design, Meddical Imaging,, Computer Biomedical
B
Enngineering andd
hics Programmiing.
Graph
Riza Sulaiman didd his Msc from
m University of
o Portmouth, UK and Ph.D
D
N
Zealand. His specializzations includee
from University off Canterbury, New
puter Aided Deesign (CAD), Medical Imagging and Roboots Simulation.
Comp
He iss working ass Associate Professor
P
in the
t
School of
o Informationn
Techn
nology , Facullty of Informaation Science and Technology, Universityy
Keban
ngsaan Malaysia.
Khatim Hasan didd his Msc from Universiti Kebangsaan Malaysia, andd
Ph.D from Universiity Putra Malaaysia. His speccializations include Scientificc
puting and Stattistical Analysiis. He is workiing as Associaate Professor inn
Comp
the Scchool of Inform
mation Technoology , Facultyy of Informatioon Science andd
Techn
nology, Univerrsity Kebangsaaan Malaysia. He
H has publishhed 108 paperss
in rev
viewed journalls and proceeddings, 3 books and chapter inn books, 12 inn
non-reviewed proceeedings and 24 technical repoorts.
Anto
on Satria Praabuwono receeived his PhD
D. in Industrial Computingg
(Macchine Vision) from Universsiti Kebangsaaan Malaysia inn 2006. He iss
currently an Associate Professor in the School of Information Technology,,
and Researcher
R
in Center for Artificial
A
Intelligence Technoology (CAIT),,
Facullty of Inform
mation Science and Technollogy, Universitti Kebangsaann
Malaaysia (UKM). He is an author
a
and coo-author for more
m
than 1200
scien
ntific papers inn Internationall Journals andd Conferences. His researchh
intereests include maachine vision, robotics,
r
and automation.
a
Abdu
ul Yazid Mohd
d Kassim is ann orthopaedic surgeon from Department off
Orthopaedic and Trraumatology, Medical
M
Centrre of Universiti Kebangsaann
ysia (UKMMC
C).
Malay
77